A motor grader is a versatile apparatus for road work, ditch work, site preparation and other surface contouring and finishing tasks. The versatility of a motor grader is provided in large part by its multiple course setting and course change options. In particular, a motor grader typically includes a steering function implemented via steerable ground engaging wheels while also allowing some degree of course correction or steering via lateral arching or articulation of the machine frame. In this manner, for example, a motor grader may be steered and articulated to follow a curve without driving the rear wheels across the area inside the curve and disturbing the just graded area.
As should be recognized from the above, motor graders are complex pieces of heavy machinery and are operatively complex. Controlling a motor grader includes numerous hand-operated controls to steer the front wheels, position the blade, control articulation, control auxiliary devices such as rippers and plows, and various displays for monitoring machine conditions and/or functions. Control of a motor grader requires highly skilled and focused operators to position the blade while controlling steering, particularly when performing curved path grading and cul-de-sac grading.
For example, in cul-de-sac grading, the operator is required to maneuver the motor grader around a substantially circular path while maintaining the blade at a desired distance from curbs and other obstacles. This requires that operators simultaneously control the blade, front wheel steering, and articulation. Failure to properly control articulation in such instances results in the front and rear portions of the machine following separate travel paths, which can cause obstacle collisions or incomplete grading requiring multiple passes.
While there are certain automatic steering solutions described for use in motor graders, these solutions do not solve the problem of maintaining proper articulation control in constant curve grading. For example, U.S. Patent Application Publication 2011/0035109 (“Steering System with Automated Articulation Control”) describes a system wherein machine articulation is automatically controlled based on machine steering. The system of the '109 application adjusts machine articulation to follow steering angles and commands, thereby maintaining tracking between the front and rear wheels of the machine.
However, when using automated articulation controls, guiding a motor grader on cul-de-sac paths or other curved paths (e.g., an “S-Curve” path) requires an operator to give small steering corrections to maintain the course of the machine. As a result of the automated articulation controls, the articulation often reacts to the small steering corrections in an undesirable manner. For example, the small steering corrections may cause the articulation to jerk or wiggle undesirably with every small steering correction. A need therefore exists to filter articulation movements for small to medium steering corrections associated with, for example, a cul-de-sac path while also avoiding filtering steering corrections when the machine is making turns.